An eyewear lens is defined as an optical part for use with the human eye. This may include non-prescription eyewear, such as store-bought sunglasses, prescription eyewear, and semi-finished lens blanks designed to be surfaced to desired prescriptions. This also may include more extreme shapes, such as goggles, visors, face shields, eye shields, helmets and the like. Lenses can be produced from a wide range of optical materials, including glass, glass-like and polymeric materials.
Eyewear lenses typically are designed to improve vision. This improvement is most commonly accomplished by use of a correcting lens that augments the eye's ability to focus light. In addition, eyewear lenses also can improve vision by reducing glare or modifying light exposure (for example, in sunglasses) to enable the eye itself to operate more effectively. Besides augmenting focus and reducing glare, an eyewear lens should ideally adjust to differing light conditions to offer improved visual acuity, regardless of any changes in light level or spectral distribution of that light (that is, the distribution of the light in the wavelengths of the visible spectrum). While certain techniques have been attempted to provide this adjustment, they have not been completely successful.
For example, electrochromic glasses have been produced that enable a wearer to adjust the transmission of the lenses independently of any external lighting. However, these glasses require battery power and/or sensors that may be cumbersome or aesthetically challenging to accommodate in aesthetically appealing fashion eyewear. Also, factors of cost, weight, environmental stability, lifetime, and optical density have been sources of difficulty for these lenses.
Lenses made from photochromic glasses also have been used. These lenses are designed to lighten and darken in response to changes in light intensity. Most stable photochromic systems are designed to respond most preferentially to ultraviolet light, to avoid unwanted darkening of the lens indoors. However, this design criterion often results in photochromics that exhibit low responsiveness in applications in which sunglasses are commonly used, such as behind the windshield of a car, because such windshields filter ultraviolet light. In addition, most photochromic lenses are designed for constant wear. Hence, to ensure that the lenses will not provide too much residual color when worn indoors, photochromic concentration of these lenses has been limited, so that they cannot attain the dark tint of conventional sunglasses, even under the brightest outdoor conditions.
Additionally, in typical lighting situations, glare due to polarized light can interfere with good vision. Glare is particularly troublesome when reflections occur from expansive flat surfaces, such as water or roadways, but it also can be a significant problem under hazy conditions, such as smoggy or foggy skies. While tints, photochromics and electrochromics all reduce total light throughput, only polarized lenses preferentially minimize glare. Hence, polarized lenses offer a unique advantage for providing improved vision. The polarized lens typically is a passive device, however, and it does not adjust optical density to varying lighting conditions. Thus, a dark polarized sunglass lens, which may reduce glare and provide sufficient transmission in full sunlight exposure, may not allow sufficient transmission under low light conditions.
Examples of lenses and related methods combining these light-modifying techniques, or including additional colorants in lenses, are known in the prior art. The visible spectral signature of polarizers has been modified by use of additional passive dyes as described, for example, in U.S. Pat. Nos. 6,382,788, and 4,878,748. However, these modifications may not be sufficient to meet expected lighting or acuity conditions, such as allowing a person wearing the lenses to clearly discern differently colored traffic lights. In addition, such passive filtering has the above-mentioned limitation of insensitivity to varying light intensities or spectral distributions. References such as U.S. Pat. No. 4,818,096 and U.S. Published Patent Application No. 2003/0075816 discuss combining photochromic materials with passive agents that modify the activated color of the resulting photochromic objects. Similarly, patents including U.S. Pat. Nos. 5,625,427 and 6,145,984 disclose combining photochromics with polarizers. As these references indicate, the main objective of prior activities has been to achieve particular constant colors, rather than to tailor the performance of the lenses for optimal visual acuity under varying lighting conditions. Similarly, U.S. Pat. No. 5,608,567 mentions that photochromics and electrochromics may complement each other, because though the photochromics may have limited response behind a car windshield, they can augment the electrochromics outdoors. The invention in U.S. Pat. No. 5,608,567 resides in using the photochromic to control the amount of light that reaches the electrochromic cell, but this mention of combination techniques, albeit with the very different technology of electrochromics, confirms that further advancements in light control are still of great interest.
Therefore, it is apparent that a need exists for optical eyewear lenses having improved response to commonly varying light conditions in comparison to lenses currently available. These lenses should not only adjust to varying light intensity, but they also should tailors the throughput of that light for optimal visual acuity. The present invention fulfills these needs and provides for further advantages.